1. Technical Field
The present invention relates to a technique for improving display quality in so-called region scan driving.
2. Related Art
Projectors that form images by using electrooptic characteristics of liquid crystal or other known materials and project the enlarged images by means of optical systems are becoming popular. A small display panel of such a projector has very narrow gaps between pixels, and thus so-called disclination (alignment defect) is a problem. The disclinatlon can be avoided by using a field inversion (also called a frame inversion) scheme, in which adjacent pixels have the same polarity. However, the field inversion scheme has a problem in which display is inconsistent between, for example, upper and lower regions of a display screen.
One approach to maintaining display consistency is disclosed in JP-A-2004-177930. In this approach, a frame period is divided into, for example, first and second periods, and a display region is divided into upper (first) and lower (second) regions. The upper and lower regions are alternately selected, and in the selected region, scanning lines are selected from top to bottom. During the first period, the upper region has positive polarity and the lower region has negative polarity, whereas, during the second period, the upper region has the negative polarity and the lower region has positive polarity. This approach is so-called region scan driving.
A projector of the above-described type itself does not have a function of generating an image. Therefore, the projector receives image data (or an image signal) supplied from a host system (e.g., a personal computer or television tuner). The image data specifies a gray scale (brightness) of a pixel for each pixel and is supplied in such a way that a matrix of pixels is scanned vertically and horizontally.
However, for the region scan driving, since the upper and lower regions are alternately selected in a continuous manner, no blanking period is present in vertical scanning of a display panel. Therefore, the region scan driving has a problem in which it is difficult to perform processing using a blanking period, for example, processing for improving display quality.